The application of corrective forces to rearrange the teeth of patients for surgical and cosmetic purposes has been accomplished in a number of ways. One traditional method of orthodontic treatment consists of applying metallic band devices around the individual teeth of the patient. Affixed to the metal band in such devices is a bracket portion designed to receive an archwire, and the device may also contain additional apertures for receiving ligating wires for the purpose of affixing the archwire securely to the bracket. Normally, the archwire is rigidly affixed to the rear teeth, such that application of a force to the rear teeth will transmit the force, by way of the archwire, to the other teeth of the patient.
Problems may arise in using metallic band devices, for example when the teeth of a patient are tightly compacted. In some cases, it is necessary to remove one or more of the patient's teeth in order to put the metallic band devices around the remaining teeth. Application of metallic bands may also result in discomfort to the patient during their installation.
Due to such deficiencies, alternate methods of affixing orthodontic appliances to a patient's teeth have been developed. Specifically, orthodontic appliances have been developed for direct affixation to the exposed face of the patient's tooth, for example by using adhesive. Such devices are affixed to the enamel on the crown of the tooth, the term "crown" referring to the enamel-covered part of the tooth which is exposed beyond the gum. Orthodontic devices of this type have been constructed of, for example, plastic, metal or ceramic.
Orthodontic devices for attachment to the surface of the tooth may be mounted onto a protective support which itself is attached to the patient's tooth. For example, U.S. Pat. No. 3,936,939 discloses a veneer supported orthodontic appliance wherein the veneer portion is affixed to the patient's tooth using adhesive. The orthodontic appliance is molded into the veneer substrate and protrudes therefrom. The devices may also be rendered aesthetically pleasing. In U.S. Pat. No. 4,470,809, an orthodontic appliance for attachment to the tooth surface is formed of molded plastic material which is colored to resemble the natural color of human teeth.
It has also been suggested that a flexible orthodontic appliance would lessen the shock of the application of force to the teeth. An example of such a device, wherein a flexible bracket member is affixed directly to the tooth or onto a metallic band, is disclosed in U.S. Pat. No. 3,052,027.
During the shifting of teeth during their rearrangement by corrective forces, it is frequently desirable to achieve actual bodily movement of the teeth and not simply a tilting or tipping movement of the teeth, a result which is not achieved by the aforesaid devices. It has been found that if the corrective force exerted by the archwire is placed on the one-third of the crown of the patient's tooth nearest the gum, a more accurate and permanent corrective result may be achieved as the bone structure of the patient heals the teeth into their new arrangement.
It has also been found that during use of available orthodontic devices, including the above-mentioned devices affixed to the surface of the tooth, food tends to accumulate on or around the archwire and/or its supporting brackets. It would, therefore, be highly desirable to provide a configuration to the orthodontic appliance which discouraged or prevented the accumulation of food on the archwire and its support means, while maintaining effective utility and comfort to the wearer.